170 KANSAS UNIVERSITY SCIENCE BULLETIN. 



which was used where possible and which proved quite satis- 

 factory in the majority of cases. The oldest material possible 

 was commonly used. 



Stains adapted to the work in hand were not found at first. 

 Iodine green and erythrosin were tried, but this method left the 

 phloem red or pink — a poor color for the purpose. Finally 

 fuchsin for the lignified walls and methyl blue for the cellulose 

 ones were found to be quite satisfactory. The latter gave a 

 fairly dark wall and slime body — the one better for making the 

 drawings, the other rendering the identification of the sieve 

 tubes less diflficult. 



The sections of such varied kind as to subject and age of 

 material stained quite differently under the same treatment, so 

 that each one usually required some variation. The slides were 

 left in the fuchsin from two hours to several days. The excess 

 stain was removed with acid-alcohol, and the slides were then 

 placed in methyl blue for from twenty seconds to three or four 

 minutes. 



As a rule, cross, radial and tangential sections, with many 

 mounts on each slide, were prepared for each subject — in all, 

 more than 300 slides. These included specimens from young 

 and from somewhat older material. The tangential sections 

 proved the best for demonstrating sieve tubes. The cross sec- 

 tions were best for the measurements of cell walls and cell 

 cavities, and to show the locality of the various tissues, etc. 

 All were used to determine, if possible, the presence of pits, or 

 of any other facts bearing on the problem. 



PLANTS EXAMINED. 



The following is a list of the plants examined, arranged ac- 

 cording to the classification of Gray's revised manual : 



Pinaceae: 



Pinus laricio Port. 

 Alismaceae: 



Sagittaria latifolia Willd. 

 Gramineae: 



Zea Mays Linn. 

 Cyperaceae: 



Scirpus validus (Vahl.) I 

 Bromeliaceae: 



Tillandsia usneoides L. 

 Liliaceae: 



Yucca glauca Nutt. 



Asparagus officinalis L. 



Smilax rotundifolia L. 



Salicaceae: 



Salix alba, var. vitellina (L.) 

 Koch. 



Populus alba L. 



Populus deltoides Marsh. 

 Juglandaceae : 



Juglans nigra L. 

 Urticaceae: 



Ulmus fulva Mx. 



Ulmus americana L. 



Celtis occidentalis L. 



Cannabis sativa L. 



Humulus Lupulus L. 



Morus rubra L. 



